In the past, polyolefin articles exhibiting antimicrobial characteristics have been manufactured by combining a plurality of pellets of a polyolefin antimicrobial composition (composition) with a resin to form a polyolefin antimicrobial mixture (mixture) that is subsequently molded or extruded during manufacture of a polyolefin antimicrobial article (article).
The composition is manufactured by compounding an antimicrobial agent into a polyolefin material (material) having a polyolefin substrate (substrate) of polyethylene (PE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ultra high density polyethylene (UHDPE), or polypropylene (PP).
The resultant composition is combined with a resin to produce the mixture. The material of the composition must be compatible with the resin utilized in the process of making the mixture. A suitable resin may be selected from the group consisting of cellulose plastics, epoxy resins, ethyl cellulose, nylons, polybutylenes, polybutyleneterephthalate, polyethylenes, polyimides, polyphenylene oxide, polypropylenes, styrene butadienes, styrene polymers and copolymers, urethane elastomers, and vinyl polymers and copolymers, or a combination of two or more of these. The mixture may subsequently be molded or extruded during manufacture of the article.
A major disadvantage associated with manufacturing the composition is that the antimicrobial agent, having polar functional group(s), exhibits a low level of compatibility with the substrate of the material. More specifically, functional groups, such as chlorine, iodine, oxygen, hydroxy, sulfone, amine and hydrochloride, of an antimicrobial agent cause the antimicrobial agent to exhibit polar properties. In contrast, the substrate of the material consists of a polyolefin, such as PE, LLDPE, LDPE, HDPE, UHDPE, or PP, having long hydrocarbon chains that are nonpolar in nature. As such, the polar functional groups of the antimicrobial agent are dissimilar, and thus insoluble, or sparingly soluble, with the nonpolar environment created by the long hydrocarbon chains of the substrate of the material. As a result, the antimicrobial agent is insoluble, or sparingly soluble, with the material of the composition.
Phase incompatibility, resulting from the antimicrobial agent being insoluble, or sparingly soluble, with the substrate of the composition may cause gross migration of the antimicrobial agent through the amorphous zones and interstitial regions of the substrate and subsequently to the surface of the substrate. Gross migration of the antimicrobial agent onto the surface of the substrate results in chalking of the antimicrobial agent on the surface of the pellets of the composition as a fine powder. When subjected to elevated temperatures, the fine powder of antimicrobial agent on the surface of the pellets has a tendency to soften and become sticky, resulting in the pellets clumping together. Clumping of the pellets of the composition during processing (i.e., compounding, physical mixing, blending, molding, extruding, packaging and shipping) is undesirable. Additionally, chalking of the composition is aesthetically unpleasing.
Leaching of the antimicrobial agent from the surface of the article, by chemical or mechanical means, may cause taste and odor issues associated with food and liquids meant for human consumption. Additionally, leaching of the antimicrobial agent from the surface of the article may subsequently result in a decrease of longevity of desired antimicrobial efficacy on the surface thereof.
Therefore a need exists for an antimicrobial concentrate that is compatible, or soluble, with the antimicrobial agent. Further needed is an antimicrobial concentrate having an antimicrobial agent that does not exhibit gross migration through the amorphous zones and interstitial regions or the antimicrobial concentrate and subsequently to the surface of the antimicrobial concentrate at high concentrations. Further needed is an antimicrobial concentrate that does not exhibit chalking and clumping of antimicrobial agent on the surface thereof. A need also exists for an antimicrobial product that does not exhibit taste and odor issues associated with food and liquids meant for human consumption, due to leaching of the antimicrobial agent from the surface of the antimicrobial product by chemical or mechanical means. Further needed is an antimicrobial product that does not exhibit a decrease in longevity of desired antimicrobial efficacy.